The Environmental Protection Agency (EPA) publishes fuel economy values that are known to be good estimates of the fuel economy a typical driver will achieve under average driving conditions. One of the fuel economy values the EPA publishes is a combined estimate, which represents a combination of city driving (55%) and highway driving (45%). A large car rental company has 16 Ford Explorers in their fleet. They collected fuel economy data from these cars and calculated the sample mean to be 23.29 mpg and sample standard deviation as 0.78 mpg. Required:
The car rental company is willing to assume that the conditions are met for constructing a confidence interval. Use the collected data to construct a 90% confidence interval for the mean combined fuel economy for Ford Explorers.